Process of making salt.



C. L. WEIL.

PROCESS OF MAKING SALT.

APPLICATION FILED MAY 31, 1911 Patented July 28, 1914.

5 :1 meadow Ckal'es Ll. [1/ 19 M wwmm J MW CHARLES L. WEIL, OF ST. CLAIR, MIGHIGAN, ASSIGNOR T0 DIAMOND CRYSTAL SALT COMIPANY, OF ST. CLAIR, MICHIGAN, A CORPORATION 01? MICHIGAN.

PROCESS OF MAKING SALT.

Specification of Letters Patent.

Application filed May 31, 1911.

11,3lll5,387.

Patented July 28, 191i. flerlel No. 630,287.

a specification.

This invention relates to processes of making salt; and it comprises a method of evaporating salt whereln brine, which may be fresh brine or tail brine, is reliminarily heated by vapors from the sci evaporation of brine in a later sta e, is then placed under pressure and is furt er heated by vapors from self-evaporation in a later stage, is again heated, is then allowed to undergo self-evaporation in a plurality of stages and is finally submitted to further evaporation, all as more fully hereinafter set forth and as claimed.

In the manufacture of salt, it is desirable to have a full control of the size of grain, a maximum evaporative efficiency in the apparatus employed and the possibility of securing a high output of crystallized salt from an apparatus of comparatively moderate size.

The object of the present invention is to secure these results by an automatic, selfregulating method of operation. purpose lrearrange the conditions of evaporation and the apparatus therefor in such a manner as to secure a methodical utilization of heat while allowing the apparatus and operation to be under full control at all times.

I advantageously supply the evaporating system with fresh brine and with tail brine from the apparatus itself in such proportion as will secure an evaporation to the exact extent desired in the material passing through the system.

in an advantageous embodiment of the present invention, a mixture of tail brine, comin from an apparatus later described, with iresh brine is transmitted through a preheater which is supplied with vapors from self-evaporation or flash evaporation occurring later in the system. This preheater is on the suction side of a pump adapted to deliver brine under some pressure. From the pump the brine goes to and For this through a second preheater where it is further heated by vapors from self-evaporation later in the system. From this second preheater, the brine may now go to and through a third heater where it may be heated with live steam, as the brine is under pump pressure, to any temperature desired. It may, for instance, be heated to 260 F, or above, according to conditions and the amount of self-evaporation later desired. Being heated under pressure, when it arrives at the temperature stated there is a tendency for the deposition of gypsum and other impurities and the brine is removed and passed throu h a filter where deposition occurs and the deposited matters are removed. From the filter, the superheated purified brine goes forward to a plurality of self-evaporators or flash evaporators. Two may be used. In these self-evaporators, the pressure is reduced in a pluralit of stages. The vapors from the first sel -cvaporator may be used to heat the second preliminary heater, while those from the second self-evaporator, which is at a lower temperature, may be used for heatin r the first preliminary heater. The first selievaporator is located on a relatively low level and is advantageously of a special type, having a salt leg and boot, provided with a conveyer. This leg should extend upwardly sufiiciently far to allow the pressure of the liquid in it to counterbalance the pressure prevailinq in this first self-evaporator. From this first self-ova orator, as shown, the brine passes upward to a second selfevaporator. By locating this second selfcvaporator at a higher level than the first self-evaporator, the pressure differential therebetwecn is rendered automatic. From the second self-evaporator, the concentrated brine may be passed into a graining pan which is as shown on the same level and may be any of the ordinary types; but is preferably of a special type provided with air agitating means for controlling the size of salt grain produced.

Air may be introduced into the solution in a plurality of minute jets, keeping it agitated and controlling the size of the grain, while at the same time aiding in evaporation. The residual or tail brine from this pan may be sent to the first preliminary heater at- I ter being. admixed with 'suficient fresh brine to bring the total concentration. to such a point as will allow the exact amount of evaporation desirable in the brine passing j through the system to the graining pan; As saturated brine boils at about 226 under ordinary atmospheric pressure, it'the brine I has been preliminarily heated to 260 there is a drop in temperature of the brlne of about 34, accompanied with a corresponding evaporation of water; flash evaporation or self-evaporation. Where a.

plurality of self-evaporators are employed, this evaporation and resulting drop in temperature is divided up among them. Pass-- ing the self-evaporated brine of 226 into the pan, further evaporation now takes place and the cooled brine passlng as tall brine into the first preliminary heater may have a temperature of about 200 F. While the vapor from brine boiling at 226 F. at ordinary pressure expands and cools to 212 E, where, as in the present invention, the

releaseoit the vapor .is under pressure, this drop in temperature does not takeplace'to such an extent. This is of importance in the present invention since more heat units canbe carried by the hotter vapor. If the pressure on the brine in'the self-evaporator be released so as to bring the temperature of the brine from, say, 260 F. to 24 5 F., steam of a temperature of 231 will be available which may be utilized in heating the same amountoif brine to a higher temperature with the same amount of heating surface than 'can be caused by an evaporator flashing steam at 212 F.

In the accompanying illustration, there is useful in. performing the process above described, and for other purposes.

In this'showing Figure l is a complete installation; and Fig. 2 is a similar fragmental view oi. a modification. I

Element 1 is the first preheater. It may be of any ordinary structure; such as that common in heat interchanges, and'heating vapor may pass either around or inside the tubes of a tube nest (not shown). Heating vapor is supplied by vapor line 2. Fresh brine which may'have advantageously been heated enters through pipe 3 while tail brine from the graining pan enters through pipe 4. The relative proportions of fresh brine and of tail brine may be controlled to bring the degree of saturation as may be desired. From this first preheater, the brine is taken by pump 5 which delivers it. under some pressure into the second preheater 6. 'The first preheater is on the suction side of the pumpland the second on the pressure side. The amount of pressure may be as desired. The second preheater is supplied with seli-evaporation steam through other impurities and the liqui inches? changer type; Tn this-superheating opera- 7 tion when the brine becomes .hot there is generally a tendency todeposit psum-and heated in passlng through the superheater is est directlp y e ryl ndri eit vess or casing partly filled w th small stoneswhi ch present a large amountofsurfaceforthe deposit of gypsum or caleium isultategzand otherimlipe'i -eomin from the eraser-evaporator v lit ated hrine goes but through passed mto and through a filter 10,

sup lied'with livesteain in amount suficient purities, carriedfbyfand.depositingirom the I superheated brine; From' 'this' device the brine, which maybei'at a temperatureof 260 F. or above,,pas sesithrough vconduit 11K to the first self-evaporator'l2, shown,

this seli-evaporatorzis on: I

level and of a particulargy e and, provided e e atively low with means for removin' II I pmtedsalt. As shown, it 1s provlded at ,hfi Y,

ing the boot. of elevating,{meansfi-ldijwhich consists of a tube, whichmay beef rectangular cross section, closed except atthe top, and provided with salt conveying mechanism, which may belcom need of chain 15;,

sprocket wheels 16' and uckets l7 carried by. the chain. The height ofthis tube should be suificient toallow the weight or the brine therein to counterbalance the pressure in the self-evaporator and allow ready removal of salt without disturbance of pressure conditions. Vapor released in this first self-evaporatoris carriedthrough a suitable conduit. (7) "to the second preheater previously described. The self-evaporated and somewhat concentrated brine leaves this selfevaporater through brine main'18 going upwardly to a second self-evaporator 19 located, as shown, at .ahigherlevel. In

this second self-evaporator another drop in.

temperature andpressure is, allowedwith a result of a turther concentration and the liberation of vapors. These vapors pass through a vapor line (2) :to thefirst preheater described, Brine is, led from this self-evaporator through conduit '20 to a graining pan 21 which may be provided with air stirring means (not shown). Tail brine from this pan goes into the first;preheater as previously described. As thereis, or may be, some formation of grai' sa l tf in this se'c- 0nd self-evaporator, it is se fullto provide I it with a depending leg 22 'passin down into the first self-evaporator and a owing the discharge of grain saltinto the latter. It is however possible, as shown in '-Fig.- 2, to make the two selfievaporators independent.

In Fig. 2, the elements are given the same reference characters as in Fig. 1. The ditference between the two figures is in the omission of depending leg 22. As shown, in Fig. 2,- the only communication between 'the first' self-evaporator 12 and the second self-evaporator 19 is through vertical brine conduit 18. In Fi 1 a double communication between 19 an 12 exists, part1 through vertical leg 22 and partly throug vertical pipe 18. Upon the height of the liquid column in 18 and 22, depends the pressure diflerential, and consequently the temperature, between 12 and 19. The difierence in hei ht automatically produces a constant di erence in temperature between the two self-evaporators. In Fig. 2 all the communication is through 18.

In the operation of the structure of Fig. 2, the hot superheated filtered brine comes in, as before, through 11. In 12 it sufi'ers a drop in temperature with a production of vapors which pass 011', as before, through 7. The brine which is now at a lower temperature passes upward through 18 into 19 to undergo a further drop in temperature and pressure. The pressure, and consequently the temperature difierential, between 19 and 12 obviously depend upon the height of the liquid column in 18. And since the height of this liquid column in 18 is set, once for all, in erecting the apparatus, the pressure and temperature difi'erent-ial between 12 and 19 is fixed; there is no necessity for the provision of regulating valves, etc.

The apparatus herein shown and described I do not claim in this application, it formin the subject matter 0 m divisional application Ser. No. 648,288 filed, Sept. 8, 1911.

What I claim is 1. The process of graining salt which comprises preheating brine by self-evaporation vapors, placing the preheated brine under pressure, further heating in successive stages to a relatively high temperature adapted to cause deposition of impurities, one such sta e being by other self-evaporation vapors and another by steam, filtering the so-heated brine, releasing the pressure on the heated brine in at least two stages in vertically separated apparatus with the brine feed from the lower to the upper in series, returning the vapors from one such stage to serve in preheating and the vapors from another such stage to aid in further heating and causing the self-evaporated brine to undergo further evaporation under atmospheric pressure to produce grained salt.

2. The process of grainin salt which comprises preheating adjuste proportions of fresh brine and of residual or tail brine from a final evaporating operation, said preheating being performed by self-evaporation vapors from a later stage, placing the preheated brine under pressure, further eating in successive stages to a relatively high temperature adapted to cause deposition of impurities, one such stage being by other self-evaporation vapors and another by steam, filtering the so-heated brine re leasing the pressure in at least two stages in vertically separated apparatus with the brine feed from the lower'to the upper in series, returning the vapors from one such stage to serve in reheating and the vapors from another suc stage to aid in further heating and causing the self-evaporated brine to undergo further evaporation under atinospheric pressure to produce grains of sa t.

3. The process of evaporating brine which comprises producing a supply of purified superheated brine at a temperature of at least 260 F., the heating of the brine being in a plurality of stages, passing such superheated brine successively from below upward throiiligh two pressure releasing devices at di erent levels, whereby the pressure diflerential is maintained constant, and releasing the pressure in each such device to produce vapors, returning the vapors to serve in producing the heated brine and delivering the brine from the pressure releasing devices into a pan for graining.

4:. The process of evaporating brine which comprises preheating brine, placing the brine under pressure, bringing to a tem erature of at least 260 F. in a p urality o successive stages, transmitting the brine thus heated through a device adapted to collect deposited matter, releasing the pressure in a plurality of stages, the release in one such stage being sufficient to cause a dro to about 245 F., transferring the heat of t e vapors from such a stage to preheated brine and returning the heat of the vapors from a following pressure-releasing stage to aid in the preheating of the brine.

5. The process of evaporating brine which comprises withdrawing self-evaporated brine from a grainer at a temperature of about 200 F., admixing with new brine, preheating the mixed brines with vapor derived from a secondary pressure-releasing stage, placing the preheated brine under pressure, raising its temperature with the aid of vapors from a primary pressure-releasing stage, further heating to bring the tem crature to about 260 F. and cause a ten ency to deposit impurities, passing the heated brine through a device adapted to collect such impurities, passing the purified brine through a primary and a secondary pressure-releasing stage to furnish the stated vapors and drop the temperature to about 226 F. and transmitting the brine to a grainer.

6. The process of evaporating brine which comprises preheating brine, placing it under pressure, further heating it to about 260 to cause a tendenc to drop impurities, passing through a device adapted to collect such impurities, releasing the pressure in a plumrality of stages with suficient evaporation in each such stage to, permit separation of salt, returning the released vapors from each such stage to aid in the heatingv operations and passing the treated brine at a tempera ture of about-226 113. into an open grainer;

Signed at St. Clair, in the county of (Hair and State of Michigan, this 27th day of May A. D. 1911.

CHAS. L, WEIL. Witnesses: LAURA MOORE,

GEORGE ALBERT SCHWAB. 

